The ichneumonid wasps (Hymenoptera: Ichneumonidae) are a fantastically diverse group of insects that mostly share a similar parasitic life history: they lay their eggs in or on a host insect. Around 24,000 species have been described, and estimates for their full diversity range between 60,000 and 100,000 species.
In Britain there are approximately 2,500 species, almost 10 times our bee diversity. Many species visit flowers, particularly umbellifers, and they can therefore be quite significant (though under-studied) pollinators of things like Wild Carrot (Daucus carota) and its relatives.
With so many species to deal with, identifying ichneumonids can be a daunting task. However the Natural History Museum (London) has produced a free beginner’s guide to identifying them – here’s a link to it.
Although it only covers 22 commonly encountered species (i.e. less than one hundredth of Britain’s species diversity) it’s nonetheless a useful introduction to a fascinating group. However you’ll not be able to identify the species pictured above – I photographed that in Tanzania a few years ago!